Folia Morphol. Vol. 63, No. 3, pp. 313–318

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Address for correspondence: Dr. Eman Elazab Beheiry, Lecturer, Department of Anatomy and Embryology, Faculty of Medicine, AlexandriaUniversity, Alexandria, Egypt, tel: 002 03 4248707, telefax: 002034844793-002034876958 (for Prof. Elazab Beheiry Elazab),e-mail: emanazab@yahoo.com

Anatomical variations of the median nervedistribution and communication in the armEman Elazab Beheiry

Department of Anatomy and Embryology, Faculty of Medicine, Alexandria University, Alexandria, Egypt

[Received 30 December 2003; Revised 18 March 2004; Accepted 24 March 2004]

Anatomical variations of peripheral nerves constitute a potentially importantclinical and surgical issue. The aim of this work is to study the variations of themedian nerve in the arm with respect to its branching pattern and distributionas well as its possible communication with the musculocutaneous and/or ulnarnerves. Sixty arms pertaining to 30 preserved human cadavers, ranging in agefrom 30 to 67 years, were dissected in pursuit of this aim. In one limb out of 60(1.7%) the median nerve gave off muscular branches to the brachialis muscle aswell as a branch from its lateral root to supply both heads of the biceps brachiimuscle. Concomitantly the musculocutaneous nerve was absent. The same limbdemonstrated a branch from the lateral cord of the brachial plexus supplyingthe coracobrachialis muscle. Three limbs (5%) showed a communicating branchbetween the median and the musculocutaneous nerves. These observationsshould be considered when a high median nerve paralysis is shown to originatein the axilla or proximal arm in a patient presenting with weakness of forearmflexion and supination. Similarly, it can explain weakness of the arm flexor mus-cles in thoracic outlet syndrome with median nerve affection.

Key words: median nerve, variations, communicating branches,musculocutaneous nerve

INTRODUCTIONAnomalies in the peripheral nerves and their con-

nections are a clinically important consideration.Patnaik et al. [18] reported that the anterolateralsurgical approach to the humerus described by Henry[8] was superior to the posterior approach describedby Berger and Backwalter [3]. Thus a thorough knowl-edge of the possible variations of the median andmusculocutaneous nerves, both branches of the bra-chial plexus [9], can be of the utmost importance inroutine surgery where such branches can be injured.

The aim of this article is to study the anatomicalvariations of the median nerve with special refer-ence to its branches, distribution and possible com-munication with other nerves, namely the muscu-

locutaneous and/or ulnar nerves in the arms of pre-served human cadavers.

MATERIAL AND METHODSThirty preserved human cadavers aged from

30 to 67 years were used. These were obtained fromthe dissecting room of the Department of Anatomyand Embryology in the Faculty of Medicine, Alexan-dria University. The axilla and arm regions of rightand left upper limbs in each cadaver were dissectedthrough an incision along the anterior axial line. Themedian nerve was studied as regards its abnormalbranches, distribution and communication with othernerves especially the musculocutaneous and/or ul-nar nerves.

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RESULTSDuring dissection of the left arm of a 65-years-

-old male cadaver the muscular branches of the me-dian nerve to the muscles of the arm were observedas follows. A branch was seen to arise from the lat-eral root of the median nerve at 1.5 cm above thepoint of union of the two roots of the median nerveand 10 cm distal to the acromion. This branch wasdivided into two branches that passed laterally be-neath the short head of the biceps brachii muscle(Fig. 1A). One of these supplied the short head ofthe biceps through two small branches. The otherpassed laterally to supply the long head of the bi-ceps brachii. A second branch arose from the medi-an nerve 16 cm distal to the acromion. It passeddownwards and laterally between the biceps brachiiand brachialis muscles and gave off three muscularbranches to the brachialis muscle. These entered themuscle at distances of 18 cm, 20 cm and 24 cm dis-tal to the acromion (Fig. 1B). This second branch

continued descending to appear at the lateral bor-der of the biceps brachii muscle in the lower arm asthe lateral cutaneous nerve of the forearm (Fig. 1B).A communicating branch between the median nerveand the previous branch was observed arising fromthe median nerve 20 cm distal to the acromion(Fig. 1B). The musculocutaneous nerve was absent.The coracobrachialis muscle was supplied by a singlebranch from the lateral cord of the brachial plexusthat entered the muscle 2 cm distal to the tip of thecoracoid process of the scapula (Fig. 1C). The rightside of the cadaver was normal and there were novascular anomalies on either side.

In the left arm of a 58-year-old male cadaver therewas a communicating branch emanating from themusculocutaneous nerve 7 cm distal to the acromi-on and 3 cm before the point where it pierced thecoracobrachialis muscle. This branch pierced thecoracobrachialis muscle with the musculocutaneousnerve and then curved medially to join the mediannerve 18 cm distal to the acromion and 13 cm abovethe medial epicondyle. Its length was 13 cm (Fig. 2).

Figure 1A. A photograph of the anterior aspect of the left arm inan adult human cadaver. The short head of the biceps brachiimuscle is reflected laterally, showing division of the branch(arrow) arising from the lateral root of the median nerve into twosubdivisions (arrow heads), one of which supplies the short headof the biceps brachii muscle (bi) through two smaller branches.

Figure 1B. A photograph of the previous specimen showinga branch (arrow) arising from the median nerve (arrow head) tosupply the brachialis muscle (br). It continues between thebiceps and the brachialis muscles as the lateral cutaneous nerveof the forearm (L). A communicating branch between the mediannerve and the previous branch is shown (c).

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On the same side there was low fusion of the tworoots of the median nerve 15.3 cm distal to the ac-romion and 15.7 cm above the medial epicondyle(Fig. 2). The right side of the cadaver was normaland there were no vascular anomalies on either side.

While dissecting the right arm of a 63-year-oldmale cadaver a communicating branch was foundarising from the musculocutaneous nerve after pierc-ing the coracobrachialis muscle 9 cm distal to theacromion. This joined the median nerve 18 cm distalto the acromion. In this arm the axillary artery wasdivided into superficial and definitive brachial arter-ies. The superficial brachial artery gave off the radialartery, while the definitive brachial artery gave offthe ulnar artery (Fig. 3). The left side was normal.

Finally, during dissection of the left arm of a 55--year-old male cadaver a communicating branch wasobserved to originate from the musculocutaneousnerve after piercing the coracobrachialis muscle7 cm distal to the acromion. It joined the mediannerve 17.5 cm distal to the acromion. No communi-cating branches between the median and the ulnarnerves appeared in any of the dissected arms.

Figure 1C. A photograph of the left axilla showing a branch (ar-row) arising from the lateral cord of the brachial plexus (Lc) andsupplying the coracobrachialis muscle (cb); A — axillary artery.

Figure 2. A photograph of the left axilla and arm regions of anadult human cadaver showing a communicating branch (c) be-tween the median (arrow) and the musculocutaneous nerves.A low fusion of the two roots of the median nerve is shown;cb — coracobrachialis muscle, bi — biceps brachii.

DISCUSSIONVariations of the nerves of the upper limb may have

clinical implications, so it is important to report themduring cadaver dissection. Abnormal electromyogra-phy (EMG) of the biceps muscle may be expected ina patient with thoracic outlet syndrome showingother evidence of median nerve affection. Similarly,a nerve conduction test of the musculocutaneous nervewould be unobtainable in the absence of this nerve.

The anatomical variations of the median nervereported in the present study include 3 main cate-gories (Fig. 4). Firstly, in one limb out of 60 (1.7%)the median nerve gave off a branch from its lateralroot to supply both heads of the biceps brachii, aswell as branches to the brachialis muscle before itcontinued as the lateral cutaneous nerve of the fore-arm. Secondly, in one limb out of 60 (1.7%) therewas absence of the musculocutaneous nerve andderivation of the nerve supply to the coracobrachia-lis muscle through a single branch from the lateralcord of the brachial plexus. Thirdly, in three limbs out

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of sixty (5%) a communicating branch between themusculocutaneous and the median nerves was ob-served. The variations of the median nerve, as well asits communication with the musculocutaneous nerve,have been reported before [5, 6, 11, 12, 20, 21].

The anatomical variations of the musculocuta-neous and the median nerves in the arm were classi-fied into 5 types [16]:• Type 1: there are no communicating fibres be-

tween the musculocutaneous and the mediannerves. The musculocutaneous nerve pierces thecoracobrachialis muscle and innervates the cora-cobrachialis, biceps brachii and brachialis muscles.

• Type 2: although some fibres of the medial root ofthe median nerve unite with the lateral root of themedian nerve to form the median nerve, some leaveto run within the musculocutaneous nerve and af-ter some distance leave it to join their proper trunk.

• Type 3: the lateral root of the median nerve runsinto the musculocutaneous nerve and, after somedistance, leaves it to join its proper trunk.

• Type 4: the fibres of the musculocutaneous nerveunite with the lateral root of the median nerveand, after some distance, emanate from the me-dian nerve.

• Type 5: the musculocutaneous nerve is absent. Itsfibres run within the median nerve along its course.In the study conducted by Kerr [13] (quoted from

[24]) on 75 brachial plexuses, the Type 5 variationwas found in 3 cases (1.7%). However, a communi-cating branch between the two nerves was observedin 18 cases (24%). Adachi [1] (quoted from [7]) re-ported a case that had a fine communication be-tween the median and musculocutaneous nerves inthe forearm, which was located posterior to the ra-dial artery at the level of the humeroradial joint. Langand Spinner [15] reported a complete fusion of themedian and the musculocutaneous nerves in a casereport. Watanabe et al. [26] found two cases (1.4%)of fusion of the median and musculocutaneousnerves among 140 upper limbs. Nakatani et al. [17]observed absence of the musculocutaneous nervewith innervation of the coracobrachialis, bicepsbrachii and brachialis muscles and the lateral borderof the forearm by branches from the lateral cord ofthe brachial plexus. Although variations reported inthe present study conformed to Type 5, the coraco-brachialis muscle was supplied by a branch from thelateral cord of the brachial plexus and not from themedian nerve. Ihunwo et al. [10] reported absenceof the musculocutaneous nerve bilaterally in a malecadaver where the flexors of the arm were supplied

Figure 3. A photograph of the anterior aspect of the right arm inan adult human cadaver. The biceps brachii muscle (bi) is reflec-ted laterally to show a communicating branch (c) between themedian (arrow) and the musculocutaneous nerves (arrowhead);cb — coracobrachialis muscle; 1 — axillary artery, 2 — superfi-cial brachial artery, 3 — definitive brachial artery.

Figure 4. Diagrammatic illustration of the anatomical variationsof the median and the musculocutaneous nerves in the presentstudy; LF — lateral cord, MF — medial cord, MC — musculocu-taneous nerve, M — median nerve, U — ulnar nerve, CB — co-racobrachialis muscle, BB — biceps brachii, B — brachialismuscle, A — communicating branch, LR — lateral root of themedian nerve, MR — medial root of the median nerve.

LF MF LF MF

LRMR

CB

BB

B

A

MC M U M U

CB

BB

B

LR

MR

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by branches from the median nerve. Similarly, Gu-musburun and Adiguzel [7] reported bilateral ab-sence of the musculocutaneous nerve in a 72-year--old female cadaver where the median nerve suppliedthe biceps brachii and brachialis muscles and alsogave off the lateral cutaneous nerve of the forearm.The coracobrachialis muscle was supplied by branch-es from the lateral cord of the brachial plexus. Therewere no vascular anomalies in this cadaver. Sud andSharma [23] reported a case of absence of the mus-culocutaneous nerve with innervation of the cora-cobrachialis and biceps brachii via the median nerve.The lateral cutaneous nerve of the forearm originat-ed from the median nerve and gave off a muscularbranch to the brachialis muscle. Prasada andChaudhary [19] reported two cases of absence ofthe musculocutaneous nerve out of 24 upper limbsdissected (8%). The median nerve took over the areaof supply of the musculocutaneous nerve by givingoff both muscular and sensory branches.

The communicating branch between the medi-an and the musculocutaneous nerves observed inthe present study could be classified as Type 2 ac-cording to Le Minor´s classification [16]. Kosugiet al. [14] reported the same finding in 43 out of 75limbs. Venieratos and Anagnostopoulou [25] stud-ied 79 cadavers and found 22 communications be-tween the median and the musculocutaneousnerves. Such communications were classified into3 types:• Type 1: the communication was proximal to the

entrance of the musculocutaneous nerve into thecoracobrachialis muscle (9/22).

• Type 2: the communication was distal to the co-racobrachialis muscle (10/22).

• Type 3: the musculocutaneous nerve as well asthe communicating branch did not pierce themuscle (3/22).Basar et al. [2] reported a case of a communi-

cating branch between the median and the muscu-locutaneous nerves in a 42-year-old male cadaver.One of the brachial veins was present between theconnecting branch and the median nerve. Uzun andSeelig [24] reported a communicating branch thatoriginated 1.6 cm distal to the origin of the muscu-locutaneous nerve and before it pierced the cora-cobrachialis muscle. It then joined the median nerveat the meeting of its two roots 20 cm above theintercondylar line of the humerus. Sarikcioglu et al.[22] reported the presence of a communicatingbranch between the median and the musculocuta-neous nerves on the right side of a 60-year-old male

cadaver in which the innervation of the coracobra-chialis muscle was mediated by an accessory nerveoriginating from the lateral cord of the brachial plex-us. Choi et al. [4] in their study of 138 cadavers(276 arms) described 3 patterns for the connectionbetween the median and the musculocutaneousnerves:• Pattern 1: fusion of the nerves (14 arms, 19.2%).• Pattern 2: one connecting branch present be-

tween the nerves (53 arms, 72.6%).• Pattern 3: two connecting branches present be-

tween the nerves (5 arms, 6.8%).A combination of Patterns 1 and 2 was observed

in one case (1.4%).

CONCLUSIONSIn conclusion, the likelihood of the median nerve

innervating the arm flexors should be consideredwhen a high median nerve paralysis takes place inthe axilla or proximal arm in a patient presentingwith weakness of forearm flexion and supination.Similarly, this variation may explain the presence ofweak arm flexors in patients with thoracic outlet syn-drome and median nerve affection. Finally, we re-port here for the first time the origin of the muscu-lar branches to the biceps brachii from the lateralroot of the median nerve.

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